Distribution of Ingested14C-Cholesterol in the Macromolecular Fractions of Rat Connective Tissues

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Abstract
The distribution of 14C-cholesterol was studied in the connective tissues of rats fed on a normal diet and on a high-cholesterol diet. The tissues studied are the skin, subcutaneously implanted polyvinyl sponge and aorta. Radioactivity and cholesterol content were determined in the chloroformmethanol extracts of these tissues as well as in macromolecular fractions obtained by their 'chemical dissection'. Semilog plots of radioactivity determined in successive chloroform-methanol extracts gave an indication of the speed of extraction of cholesterol from the tissues studied. This speed was about equal for skin and sponge tissues and significantly higher for aorta; it was not influenced by the regime or by the sex of the animals. The first two chloroform-methanol extracts contained over 95 % of the total radioactivity. The remaining radioactivity showed non-random distribution between the macromolecular fractions of the tissues. A significant fraction of radioactivity remained associated with the polymeric fibrous stroma (several times extracted with 1 M CaC12) containing mainly collagen, structural glycoproteins and elastin. The fraction of radioactivity associated with elastin was significantly increased in the high cholesterol diet groups. The specific activity of tissue-cholesterol varied between large limits and was significantly different from the blood serum cholesterol. Especially high specific activities were found in the residual cholesterol fraction associated with elastin. These results support the assumption of several separate, slowly equilibrating tissue pools of cholesterol and suggest that the cholesterol associated with the macromolecular components of the intercellular matrix (elastin, collagen, structural glycoproteins) may represent such separate pools.